From: Torsten.Lif@eos.ericsson.se (Torsten Lif) Date: Mon, 8 Feb 93 12:35:55 +0100 Subject: Rear fairings On the recent line of fairings - does anybody have numbers or opinions on the relative values of front and rear fairings (for speed purposes only)? There's an English SWB, the KingCycle, which has a combined storage box and rear fairing behind the backrest. I suppose you can say it's an aerodynamically built rear carrier. This both looks neat and seems easier to install than a front fairing. Yes, I know it does not protect you against the elements (no need to remind ME of the weather - we just barely don't have any snow here for the moment) but does it reduce aero drag to any significant amount? /Torsten From: "Richard Taylor" Date: Mon, 8 Feb 93 12:31:52 +0000 (GMT) Subject: Re: Rear fairings > > > On the recent line of fairings - does anybody have numbers or opinions > on the relative values of front and rear fairings (for speed purposes > only)? There's an English SWB, the KingCycle, which has a combined > storage box and rear fairing behind the backrest. I suppose you can say > it's an aerodynamically built rear carrier. This both looks neat and > seems easier to install than a front fairing. Yes, I know it does not > protect you against the elements (no need to remind ME of the weather - > we just barely don't have any snow here for the moment) but does it > reduce aero drag to any significant amount? > > /Torsten > > > although I am no expert on fairings, I did soem work many moons ago on computational fluid dynamics & the group I was working with were looking at the effect of the rear of a car on overall drag. The shape of the rear "fairing" on the car had a very major effect, and not always in an ovious way. A sharp cutof (such as the seat on your hpv) often had a detrimental effect if the front fairing had not been designed properly Richard --- ,_~o Dr. Richard Taylor email : rwt@uk.ac.york.ohm _-\_<, CSEG, University of York tel : (44) 904 432351 (*)/'(*) Y015DD, England fax : (44) 904 432335 From: "Nickolas E. Hein" Date: Mon, 8 Feb 93 6:21:37 PST Subject: Re: Rear fairings > > > > > > > > > On the recent line of fairings - does anybody have numbers or opinions Now here's something I know something about. In a report on automotive aerodynamics published by the Society for Automotive Engineers (SAE) a few years ago the following wind tunnel results were shown for several bodies with the same volume: Object Relative drag Flat Plate : 1.0 Brick : 1.2 w/tail fairing : 1.1 w/nose fairing : .2 teardrop shape : .1 Note that the tail fairing changes the drag by .1 no matter what the rest of the vehicle looks like, but depending on what you compare it to it either looks like a %10 or a %50 difference. The upshot of it is that you should streamline the nose first if you want really noticeable drag improvement, streamlining the tail is only worth doing after everything else has been treated. Hope this helps. Nick. (I am quoting these numbers from memory, I'll try to find the article if requested, but I'm certain of the conclusions.) -- I take responsibility for everything I say, that's my problem. But I could be completely wrong, that's your problem. ============================================================================= Nickolas Hein | Voice: (206) 662-4972 Boeing Commercial Airplane Group | Boeing net: neh3568@aw101.iasl.ca.boeing.com P.O. Box 3707, M/S 19-MK | Snail Mail: 12829 SE 184th st Seattle, WA 98124-2207 | Renton WA 98058 ============================================================================= From: R.Stclair@EBay.Sun.COM (R D St.Clair) Date: Mon, 8 Feb 93 16:43:17 PST Subject: Re: Rear fairings My personal experience agrees with nick's numbers. Tail fairings are of dubious value as far as aerodynamics goes, especially if there is a sizable gap between the front and rear fairing. If the front and rear fairing are combined (fully faired with no gap) the aerodynamics are slightly better. Therefore I would say the reasons for having a rear fairing are mostly: 1. It makes an enclosed place to store junk. 2. It looks way cool. In other words it's probably not worth the weight, unless you: 1. Keep it very light, i.e. spandex over aluminum tube frame. 2. Make it lockable weather tight storage. 3. Don't ride on hills. 4. Don't care about the weight. Thanks, R.D.